WDPS31 PGTW 142100
MSGID/GENADMIN/JOINT TYPHOON WRNCEN PEARL HARBOR HI//
SUBJ/PROGNOSTIC REASONING FOR TROPICAL CYCLONE 30P (THIRTY) WARNING 
NR 003//
RMKS/
1. FOR METEOROLOGISTS.
2. 6 HOUR SUMMARY AND ANALYSIS.

SUMMARY:
   INITIAL POSITION: 18.0S 168.9E
   INITIAL INTENSITY: 40 KTS
   GEOGRAPHIC REFERENCE: 39 NM EAST-SOUTHEAST OF PORT VILA, VANUATU 
   MOVEMENT PAST 6 HOURS: SOUTHEASTWARD AT 14 KTS
   SIGNIFICANT WAVE HEIGHT: 20 FEET

SATELLITE ANALYSIS, INITIAL POSITION AND INTENSITY DISCUSSION:
ANIMATED ENHANCED INFRARED (EIR) SATELLITE IMAGERY DEPICTS A 
PARTIALLY-EXPOSED LOW-LEVEL CIRCULATION CENTER (LLCC), WITH A LARGE 
CENTRAL DENSE OVERCAST FORMING OVER THE LLCC. A 141835Z WSFM 89GHZ 
COLOR COMPOSITE MICROWAVE IMAGE REVEALS SHALLOW CONVECTIVE BANDING 
WRAPPING INTO A BROAD, DEFINED LLCC, WITH DEEP CONVECTIVE BANDING 
OVER THE EASTERN SEMICIRCLE. SURFACE OBSERVATIONS FROM PORT VILA 
(NVVV) INDICATE LIGHT WEST-NORTHWESTERLY WINDS, WHICH SUPPORTS THE 
INITIAL POSITION, AND A MINIMUM SLP VALUE OF 996MB. ENVIRONMENTAL 
ANALYSIS INDICATES A FAVORABLE ENVIRONMENT WITH ROBUST POLEWARD 
OUTFLOW, WARM SST VALUES AND LOW VERTICAL WIND SHEAR. THE INITIAL 
INTENSITY IS ASSESSED AT 40 KNOTS, SLIGHTLY HIGHER THAN THE PGTW 
DVORAK ESTIMATE, BASED ON RECENT SCATTEROMETER DATA.   

INITIAL WIND RADII BASIS: OBTK 

CURRENT STEERING MECHANISM: WESTERN PERIPHERY OF A DEEP-LAYER 
SUBTROPICAL RIDGE (STR) POSITIONED TO THE EAST.

AGENCY DVORAK AND AUTOMATED FIXES: 
   PGTW: T2.5 - 35 KTS
   KNES: T2.0 - 30 KTS
   CIMSS ADT: 49 KTS AT 141800Z
   CIMSS AIDT: 39 KTS AT 141800Z
   CIMSS PRINT: 40 KTS AT 141700Z

FORECASTER ASSESSMENT OF CURRENT ENVIRONMENT: FAVORABLE
   VWS: 10-15 KTS
   SST: 28-29 CELSIUS
   OUTFLOW: STRONG POLEWARD AND EQUATORWARD

ANALYSIS CONFIDENCE:
   INITIAL POSITION: MEDIUM
   INITIAL INTENSITY: MEDIUM
   INITIAL WIND RADII: MEDIUM

3. FORECAST REASONING.

SIGNIFICANT FORECAST CHANGES: THERE ARE NO SIGNIFICANT CHANGES TO
THE FORECAST FROM THE PREVIOUS WARNING.

FORECAST DISCUSSION: TROPICAL CYCLONE (TC) 30P IS FORECAST TO TRACK
SOUTHWARD THROUGH THE FORECAST PERIOD, ALONG THE WESTERN PERIPHERY OF 
THE STR. TC 30P WILL MERGE WITH A LARGE MIDLATITUDE LOW, WITH A TIGHT 
GRADIENT OVER THE SOUTHEASTERN PERIPHERY FORECAST TO PRODUCE STORM 
FORCE WINDS REACHING 50-60 KNOTS. AS THE SYSTEM TRACKS SOUTHWARD, IT 
WILL QUICKLY TRANSITION INTO A SUBTROPICAL LOW AS IT TRACKS UNDER THE 
SUBTROPICAL JET AND INTERACTS WITH THE BAROCLINIC ZONE.  

MODEL DISCUSSION: NUMERICAL MODEL TRACK GUIDANCE IS IN GOOD AGREEMENT 
WITH A 150 NM CROSS-TRACK SPREAD AT TAU 36 AND MINIMAL ALONG-TRACK 
SPREAD BETWEEN TRACKERS. THE 141200Z ECENS AND GEFS ENSEMBLES ARE IN 
GOOD AGREEMENT ON THE TRACK FORECAST THROUGH TAU 36 AND SHOW HIGH 
POTENTIAL FOR STORM FORCE WINDS AS THE SYSTEM TRACKS TOWARD NEW 
ZEALAND.   

FORECAST CONFIDENCE:
   TRACK 0 - 72 HR: HIGH
   INTENSITY 0 - 72 HR: MEDIUM//
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